Ammeter



(No Model.) 2 Sheets-Sheet 1. M. GARVER. AMMETER Patented'Apr. 8

HVVE/VTUI? a/au /b WITNESSES.-

A; AZ'ZZVEY (No Model. 2 Sheets-Sheet 2 M. M. GARVER.

AMMETER.

Patented Apr. 8, 1890.

M ATTORNEY UNITED STATES MADISON M. GARVER, OF

PAT NT OFFI E.

NEWARK, NEW JERSEY.

AMMETER.

SPECIFICATION forming part of Letters Patent No. 425,069, dated April 8, 1890.

Application filed December 14,1889. Serial No. 333,769. (No model.)

To all whom it may concern:

Be it known that I, MAmsoN M. GARVER, of Newark, Essex county, New Jersey, have invented a new and useful Improvement in Ammeters, of which the following is a specification.

My invention relates to an ammeter for measuring the strength of an electric current.

My invention consists in the novel con struction of the instrument, in which in lieu of the coil of wire usually employed, through which the current is passed, a bar of conducting material is substituted. Through said bar, and free to turn therein, extends an arbor,.which carries two magnets, preferably semicircular in form, and having their opposite polar faces opposed and in close proximity to opposite sides of said bar. In each face of the bar and in the area swept over by the magnets when the arbor rotates is formed a countersink or recess, or the bar is made of less thickness atsaid portion in any other suitable Way, so that the interval between themagnet-poles is decreased. In this manner the bar is caused to pass through a very intense magnetic field and the sensitiveness of the instrument greatly increased. The rotary movement of the arbor is opposed by springs, which return the index to the zero position when the current ceases.

In the accompanying drawings, Figure 1 is a top view of the instrument. Fig. 2 is a transverse section on the line X X, Fig.1. Fig. 3 is a transverse section on the line Y Y, Fig. 1. Fig. 4% is a top view of the conducting-plate, showing in detail a means of varying theproportion of current passing through the thin portion of the plate which enters between the magnets; and Fig. 5 is a section on the line Z Z of Fig. 4.

Similar letters and figures of reference indicate like parts.

A is the base of the instrument, containing a chamber or recess 13 for the reception of the bent bar 0. The bar 0 is of conducting material and takes the place in the instrument of the ordinary coil of thick wire used in ammeters generally. Its extremities extend under the upper wall of the chamber B, and are secured by screws D to the binding-posts 1 and 2. These binding-posts have cylindrical portions E, which extend down through said walls, with which portions the extremities of the bar 0 are held in close contact by the screws D, before named. The middle portion G of the bar C extends upwardly through an opening F in the chamber B. At the center of said middle or elevated portion G are made circular countersinks opposite to one another and on opposite sides of said bar, so that the portion H between said countersinks is rendered thinner than the rest of the bar. Through a central opening in said thin portion passes a vertical arbor I. Entering the ends of said arbor are two pivot-pins I, the extremities of'which are received in the extremities of the adjustingscrews J K, which pass through threaded apertu res in the ends of the brackets L M. The brackets L M are secured by screws N on opposite sides of the bar 0. Extending from the brackets J K are bent arms 0 P, to which are attached the extremities of coiled springs Q R, the other ends of which are fastened to the fixed collars S on the arbor I. Also upon the arbor I and below the spring Q, is secured a light disk T, which supports an index-needle U. In Fig. 1 the disk T is omitted and the needle shown directly secured to the arbor. The needle U moves over a scale-plate V, which is supported upon bracket WV, attached to the bar 0. The arbor I carries two permanent magnets to b, semicircular in form and having their oppositely-named poles facing. The upper magnet a has its polar extremities entering the countersink on the upper side of the bar 0, and in close proximity to the thin portion H. The lower magnet 11 enters the countersink on the lower side of the bar 0 and has its polar extremities exactly opposite the polar extremities of the magnet a and in close proximity to the thin portion II. The purpose of the two countersinks in the bar 0 producing the thin intermediate part II will now be apparent, the object being to allow the poles of the magnets to be brought into very close proximity to one another.

The circuit in the instrument proceeds from the binding-post 1, through the bar 0, to the binding-post 2, or vice versa.

The following advantages result from the above-described construction:

First. No wire coil is used in the instrument, but in place thereof is substituted the easily-made bar 0.

Second. The magnets a and b may be made in the form of a ring of suitable steel, which may be cut in two diametrically after tempering and before magnetization. In this way I am enabled to produce magnets closely alike in strength, and so more nicely determine the astatie quality of the apparatus.

Third. 13y reason of the semicircular form of said magnets I can bring their respective polar extremities of opposite names into close juxtaposition, allowing only enough space between them to accommodate the thin portion 11 of the bar. I thus produce an intense magnetic field between said poles, which field is intersected by the field due to the current traversing the portion H of said bar. I thus augment the sensitiveness of the instrument.

Fourth. By making the magnets of comparatively heavy steel bars I increase the m agnetic effect and render the same more permanent than is the case with the ordinary thin and light parallel needles of an astatic galvanometer.

Fifth. The mode of suspension of the magnets is exceedingly delicate and prevents any displacement of said magnets laterally. By means of the screw-pivot bearings J' K the arbor I may be raised or lowered, so as to adjust the magnets with reference to the thin portion II of the bar 0-.

Sixth. All of the working parts are simple, few, and easily separated or assembled.

The operation of the instrument is as follows: hen the current passes through the bar C, the magnets a and l), in accordance with well-known laws, tend to place themselves at an angle to the longitudinal axis of the bar, which angle is determined by the strength of the current and by the opposition offered by the springs Q, and R. The opposing force of the springs by reason of their form is practically constant. The position of the magnets is shown by the index-needle U. It remains simply to calibrate the instrument and to lay off a suitable scale on the plate V, which scale may he graduated in amperes or fractions thereof. It will be apparent that the strength of the current passing through the thin portion II of the bar C will depend, other things being equal, upon the thickness of said thin portion, and therefore I may govern the sensitiveness of the instrument by increasing or diminishing said thickness in constructing the bar C. A more convenient way, however, of regulating the sensitiveness of the instrument is by controlling the proportion of current which passes through the thin plate H as compared with the remaining and thicker portion of the bar C, and for this purpose I prefer to use the device shown in Figs. 4 and 5. In the edges of the bar C are tapped two holes, in which are inserted the screws 0 (Z. It will be clear that when these screws are inserted to their full extent then the maximum proportion of current will pass through the thicker portions of the bar 0 on each side of the thin portion H; but when the screws are drawn out then less current will pass through said thick portions of bar C and more current will pass through the thin portion II. In this way a nice adjustmentof the proportion of current allowed to pass through the thin portion H may be made.

By the term polar extremity of the magnet as herein used I mean the end face of the magnet in con tradistinction to the surface on either side, or, in other words, that face of the magnet which is at an angle to the longitudinal axis thereof, if the magnet be regarded as straightened out and not parallel to said axis. The advantage of placing the polar extremities of the magnet in proximity to the surface of the conductor is that a very much more intense field of force is produced by the magnet directly at its polar extremities than at points along its length on either side thereof, and hence, through the reaction of this field of force upon the field of force produced around the conductor by the current, I attain a greater sensitiveness of the needle than would be possible if the needle were arranged with its polar extremity practically at right angles to the surface of the conductor instead of parallel thereto. The distinction between the arrangement of my magnet-needle with its polar extremities facing the surface of the conductor and. the arrangement of the ordinary galvanoineter magnet not having its polar faces so placed will be readily apparent on comparing the needle of my device with the needle of any ordinary astatic galvanometer.

I claim- 1. In an electrical measuring-instrument, a conducting-body and a magnet rotary on an axis perpendicular to the surface of said body, the said magnet having its polar extremities in proximity to and facing said surface.

2. In an electrical measuririg-instrument, a conducting-bod y and a curved magnet rotary on an axis perpendicular to the surface of said body, the said magnet having its polar extremities in proximity to and facing said surface.

3. In an electrical measuring-instrument, a conducting-body, an arbor passing through said body perpendicular to the surface thereof and free to turn therein, and a magnet secured to said arbor and having its polar extremities in proximity to and facing said surface.

4. In an electrical measuring-instrument, a conducting-body, an arbor passing through said body perpendicular to the surface thereof and free to turn therein, a magnet secured to said arbor and having its polar extremities in proximity to and facing said surface, and means for adjusting said magnet nearer to or farther from said surface.

5. In an electrical measuring-instrument,a

conducting-body, an arbor passing through said body perpendicular to the surfacethereof and free to turn therein, a magnet secured to said arbor and having its polar extremities in proximity to and facing said surface, and means for moving said arbor longitudinally.

(5. In an electrical measuriug-instrument, a conducting-body, an arbor passing through said body perpendicular to the surface thereof and free to turn therein,a magnet secured to said arbor and having its polar extremities in proximity to and facing said surface, two fixed supports, and in said supports bearings or steps receiving the extremities of said arbor, the said steps being adjustable in the direction of the axis of said arbor.

7. I11 an electrical measuring-instrument, a conducting-body having parallel opposite surfaces and two magnets rotary on a common axis perpendicular to said faces, the said magnets having their unlike poles opposed and respectively having their polar extremities in proximity to and facing said opposite sur faces.

8. In an electrical measuring-instrument, a

conducting-body having parallel surfaces, an

arbor passing through said body perpendicular to said surfaces and free to rotate therein,

and two magnets with unlike poles opposed secured to said arbor 011 opposite sides of said body, and respectively having their polar extremities in proximity to and facing said opposite surfaces.

9. I11 an electrical measuring-instrument,a conducting-body having in its surface a recess or countersink and a magnet rotary on an axis perpendicular to said surface, and having its polar extremities entering said recess or countersink and in proximity to and facing the bottom thereof.

10. In an electrical measuring-instrument, a flat conducting-body having a circular recess or countersink in its surface and a curved magnet rotary on an axis perpendicular to the surface of said body, and having its polar extremities entering said recess or countersink and facing and in proximity to the bottom thereof. v

11. In an electrical measuring-instrument, a conducting-body having parallel opposite faces and in each face a recess or countersink, said recesses being opposite one another, and two magnets rotary on a common axis perpendicular to said faces, the said magnet shaving their unlike poles opposed and respectively having their polar extremities in proximity to and facing the bottoms of said countersinks.

12. In an electrical measuring-instrument, a flat conducting-body and a magnet free to turn on an axis perpendicular to the surface of said body and disposed in inductive proximity thereto, and means for varying the relative proportion of current passing through the mass of said body included within the area swept over by said magnet in turning and through the mass of said body without said area. 7 V

13. In an electrical measuring-instrument, an elongated conducting-body and a magnet free to turn on an axis perpendicular to the surface of said body and disposed in inductive proximity thereto, and means for varying the electrical resistance of that portion of said body laterally without the area .swept over by the magnetto a current passing longitudinally through said body.

14. In an electrical measuring-instrument, a conducting-body and a magnet free to turn on an axis perpendicular to the surface of said body and disposed in inductive proximity thereto, that portion of said body included within the area swept over by said magnet during its turning being of less thickness than the remainder of said body.

15. In an electrical measuring-instrument, an elongated conducting-body and a magnet free to turn on an axis perpendicular to the surface of said body and disposed in inductive proximity thereto, the portion of said conducting-body included within the area swept over by the magnet during its turning offering a greater electrical resistance to the passage of a current lengthwise said body than the port-ion of said body laterally adjacent to said area.

16. In an electrical measuring-instrument,

a conducting-body having parallel opposite faces and two magnets rotary on a common axis perpendicular to said faces, said magnets having their unlike poles opposed and their polar extremities in proximity to and facing said opposite faces, the said body being of less thickness within the area swept over by said magnets than elsewhere.

17. The combination, in an electrical measuring-instrument, of a bar or plate 0, of conducting material, arborI, passing transversely through said bar and free to turn therein, a permanent magnet supported on said arbor and having its polar faces parallel to and in inductive proximity to the surface of said plate, and a spring connected to said arbor and opposing its rotation.

18. The combination, in an electrical measuring-instrument, of a bar or plate C, of conducting material, arbor I, passing transversely through said bar and free to turn therein, a permanent magnet supported on said arbor and having its polar faces parallel and in inductive proximity to the surface of said plate, an index-needle secured to said arbor, and a fixed scale for indicating the deflection of said needle.

19. The combination, in an electrical measuring-instrument, of a bar or plate 0, of conducting material, an arbor I, passing transversely through said bar, two magnets respectively supported on said arbor and having their unlike poles opposed and their polar faces parallel and in inductive proximity to oppo- IIO site surfaces of said bar, a spring connected to said arbor and opposing its rotation, an index-needle secured to said arbor, and a scale for showing the deflections of said needle.

20. The combination, in an electrical measuring-instrument, of the bar 0, of conducting material, brackets L M, secured on each side of said bar, arbor I, having its bearings in said brackets and passing through said bar, magnets CL 1), secured to said arbor and having their opposite poles facing one another and disposed 011 opposite sides of said bar, spring S, attached to said arbor and to an abutment supported by one of said brackets, an indexneedle secured to said arbor, a scale for showing the deflections of said needle, and circuitconnections.

21. The combinatiomin an electrical measuring-instrument, of the conducting-bar C, having the thin portion H, a magnet (1 having its polar faces in inductive proximity to said portion II and supported so as to be free to turn on an axis perpendicular to the surface of said bar, and a screw or plug 0, entering said bar and adjustable therein.

22. The combination, in an electrical measuring-instruinent, of the conducting-bar (l, having the thin portion H, a magnet a, having its polar faces in inductive proximity to said portion II and supported so as to be free to turn 011 an axis perpendicular to said bar, and screws or plugs a (Z, entering and adj ustablc in said bar on opposite sides of said thin portion H.

MADISON M. GARVER.

\Vitnesses:

JAMES S. GREvEs, M. BoscH. 

